Question: If $x \bigtriangleup y = 4x-7y$ and $x \diamond y = 7y+4$, find $(-2 \diamond -1) \bigtriangleup 1$.
Explanation: First, find $-2 \diamond -1$ $ -2 \diamond -1 = (7)(-1)+4$ $ \hphantom{-2 \diamond -1} = -3$ Now, find $-3 \bigtriangleup 1$ $ -3 \bigtriangleup 1 = (4)(-3)-(7)(1)$ $ \hphantom{-3 \bigtriangleup 1} = -19$.